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v6 go into v4 mode much?

44K views 77 replies 37 participants last post by  GraniteBlue05 
#1 ·
My 2017 Colorado 4X4 Z71 almost NEVER goes into V4 mode.
The only time it will is upon deceleration - and after a few seconds, it goes back to V6.

I have a SS camaro that has same technology and it goes from V8 to V4 - it does it all of the time as long as I'm not accelerating very hard.

In my camaro, I can be going 70mph on the interstate and as long as there isn't a HUGE head wind or i'm going up hill.. it stays in V4 mode for ever...

I'm puzzled.
 
#45 ·
OK, I understand gaming the EPA. I also understand physics. But will one of you experts out there please explain to me what AFM 2 cylinder deactivation on brief deceleration accomplishes in real numbers?

I am having a difficult time believing this is just another manufacturer/government charade at the consumers expense.

Why not go max on fuel efficiency, shut down the engines entirely and just tow these trucks from point to point.
 
#47 ·
Note that I am not a proponent of the cylinder deactivation. I remember a buddy's father back in the late 70s had one of those Cadillac setups, and while looking at the all of the technology on the instrument panel, it seemed pretty hard to fathom how it would work.

I do think that if you have a 5.3L V8 and can run it somehow in a V4 mode, their might be substantial savings.

I also think the only way the cylinder deactivation really works is if you can run on 4 cylinders for extended periods of time. If the only time these engines see enough of a reduced demand to run on 4 cylinders is downhill with the wind at your back as you decelerate, then it isn't worth it.

I'd love to drive one of these on a couple of good roads where I know I can "hypermile" the truck and see if I can get substantial 4 cylinder operation.

In any event. I think this is a great selling feature, to choose the diesel.
 
#50 ·
Why not go max on fuel efficiency, shut down the engines entirely and just tow these trucks from point to point.
That would not be more efficient, taking into account the tow truck.

Cylinder deactivation should reduce fuel consumption during idle. Six cylinders aren't necessary just to keep the engine running. I don't see why anyone should be opposed to this on principle. It is just a matter of whether the system works well or not.
 
#52 ·
Does the engine go into V4 mode when sitting at a light?



That is an interesting angle I had not considered, as I was more focused on driving down the road on 4 cylinders. With all of the idle time I see on my afternoon drive home, I could see some real savings in V4 mode. (I still want more excuses to consider a diesel in 2020 when I replace my truck. )


Mine is in v4 when you are stopping. As soon as I'm stopped idling it goes back to v6. Terrible design.



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#54 ·
Mine is in v4 when you are stopping. As soon as I'm stopped idling it goes back to v6. Terrible design.



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Many of the comments I have read have suggested the only time it was going into V4 mode was when the truck was decelerating. This makes sense, not sure why this design is so terrible, unless the delay to wake up the other two cylinders is noticeable.
 
#49 ·
The simple answer would be 2/3 of the full engine specs, but since you are driving two "dead" cylinders, probably closer to half perhaps?
 
#55 ·
lol. . I think it quit working only with people who tweet and FB a lot and want to know things instantly without exerting much effort or thinking.

You know. .. "Tell me what I want to know. . . tell me right now! I don't want to take the time to think or look things up myself."
 
#60 ·
Mine goes V4 on deceleration. It also will go into V4 on level ground and going down hill under light throttle.

It will kick into V6 around 25-30 MPH to stop. It also will not kick in till warmed up.


The reason it will not go to V4 at stop may have to do with the fact they are wanting to keep the idle smooth.


Note most DI injection engines do not use fuel as long as you are off throttle. It will cut the fuel off coasting and as long as you remain in gear. That was what I was told by a GM Powertrain engineer a when it came out.


You can pick up noticeable miles when you get totally off throttle coasting. Most of us will keep on the gas just a little and that activates the gas flow.


Now with that said the system is tuned to the truck and to the things you do with the truck. I do notice that when driving in ways or places the V4 kicks in the gas MPG does respond.


Lets put this into perspective. I own a Denali Canyon Crew short bed 4x4. I see 19.5 City driving to work. My last truck was a Sonoma Extended cab with the same 3:42 gear but only two wheel drive and with the 192 HP 4.3. It got 18 MPG on a cold day and 19 on a warm day with the AC off.


To be honest the MPG is great on the much heavier and powerful Denali vs. my old Sonoma. Also the engine is much smoother and it has better acceleration. For 4500 pounds it is better than we have ever seen in the past.


I expect the auto stop will appear at some point in the near future. Not a fan but it works well. The main gripe I have is most times it is on a 4 cylinder and it has a shake to it when you start up pulling away. It is just the 4 cylinder shake and not much you can do to eliminate it. I ponder the V6 may do better with it?


As for the V4 I do see the difference it does make and it works seamlessly. If it were not for the indicator you could not tell when it is in or out.
 
#61 ·
The reason it will not go to V4 at stop may have to do with the fact they are wanting to keep the idle smooth.
Yep, the motor is not balanced to idle on 4 cylinders, the thing would be vibrating like crazy.
 
#67 ·
What's the point of switching to V4 mode if the engine isn't delivering power? Does switching to V4 save that much gas during idle? It seems odd to me that it isn't capable of propelling itself with 4 cylinders, even in city driving 25-35mph, as it should be more than enough unless you pounce on the gas.
 
#68 ·
Oh .. it does power the vehicle somewhat. The engine goes into V4 mode under light loads like driving along at slower speeds (25 to 35 MPH or so) in town and even at highway speeds I've seen it drop into V4 mode at 60 to 65 on level terrain or very slight long down hill grades. . .. again when the engine is under light load and little gas pedal.
I guess the theory , on paper, is that under light engine load why use fuel in 2 of the cylinders ?::chevy::
 
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#71 ·
With stock gears I would only see V4 when less than 2-3% throttle, now with 4.10's I see V4 more often and can go 5-8% throttle before kicking out. I see it speeds from 15 to 75 mph.
 
#76 ·
The mistake is that many think this is about MPG.

The real reason for this is more about the off cycle credits the MFGs earn. The fuel saving is there but negligible. But the credits earned by the MFGs are great.

The system works today mostly due to the computer abilities we have today. Killing odd the cylinders mechanically was not difficult but getting it so work seamlessly was difficult.

Today’s sensors and computers are light years ahead of what we had in the 80’s.

The off cycle credits are more about emissions that can not be measured in normal driving and the government awards credits base on the added technology.

Here is something that better explains what is going on today with some of the technology we are seeing used.

https://www.theicct.org/sites/defau...ycle-Credits_ICCT-White-Paper_vF_20180327.pdf

These credits are widespread in what is counted and how they are used. Everything from cooling seats, paints, cylinder drop, special glass etc can be counted.

So if something that makes little sense is being used that appears to not save much gas it may be more for emissions.

The Start Stop systems are a part of the Off Cycle program too. It is another thing seen as cutting emissions.

Automakers may market the as fuel saving as they may to a small degree but most of this is due to emissions.

4 cylinders polite less than 6 or 8 when not under power.
 
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